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Estimating the magnitude of bankfull flows for streams in Idaho

Water-Resources Investigations Report 2003-4261

Prepared in cooperation with U.S. Department of Agriculture, Forest Service
By:
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Abstract

Methods for estimating magnitudes of peak flows with recurrence intervals of 1.5 and 2.33 years were developed for ungaged sites on streams throughout Idaho. These peak flows represent the magnitudes at and near bankfull stage and are needed for quantification of water rights required to maintain or restore fish and wildlife habitats and riparian vegetation. Data from a previous report detailing methods for estimating magnitudes with recurrence intervals of 2 to 500 years were used in this study. Generalized least-squares regression techniques were used to calculate the final coefficients and measures of accuracy for the regression equations for each of nine regions. The equations relate basin and climatic characteristics to peak flows with recurrence intervals of 1.5 and 2.33 years. The basin and climatic characteristics used to develop the equations included drainage area, mean basin elevation, forested area, mean annual precipitation, basin slope, north-facing slopes greater than 30 percent, and slopes greater than 30 percent. Average standard errors of the regression model ranged from +150 to -60.1 percent, and average standard errors of prediction ranged from +165 to -62.2 percent. The range of prediction errors was narrowest, -48.9 to -32.9 percent, for region 5. A computer program was developed to automate the calculations required for the regional regression calculations. Results from this program comprised calculated peak flows, site-specific standard errors of prediction, and the 90-percent confidence intervals for the estimates.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Estimating the magnitude of bankfull flows for streams in Idaho
Series title:
Water-Resources Investigations Report
Series number:
2003-4261
Edition:
Revised June 16, 2004
Year Published:
2004
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Idaho Water Science Center
Description:
iv, 36 p.
Number of Pages:
42
Country:
United States
State:
Idaho;Montana;Nevada;Oregon;Washington;Wyoming
Scale:
2000000